Direct or Inverse Variation

Which of the following represents direct variation?

• y = kx

• y = k/x

• y = x/k

• y = mx + b

Y varies directly with x, and y is 84 when x is 16. Which equation represents this situation?

• y=1344x

• y=100x

• y=5.25x

• y=4/21x

The width of a rectangle varies inversely with its length.  If the width is 6 when the length is 24, give an equation that shows the relationship.

• y = 4x

• y = 144x

• y = 4/x

• y = 144/x

The Height of a wave in California varies directly with the seconds that pass by.  At 4 seconds, the wave is 6 feet high.  How many seconds will give you a wave that is 10 feet high? 

• y = 2/3x

• 6

• 6.6

• 7

If x and y are in an inverse variation then which of the following is correct?

• x - y = constant

• x + y = constant

• xy = constant 

• x⁄y is constant 

Y varies inversely with x, and y is 0.5 when x is 4. Which equation represents this situation?

• y=2x

• y=2/x

• y=4x

• y=x/2

Y is directly proportional to the square of z and inversely proportional to w.

• y=kz²/w

• y=kz/w

• y=w/kz²

• y=w/kz

The number of kilograms of water in a person’s body varies directly as the person’s mass.  A person with a mass of 90 kg contains 60 kg of water.  How many kilograms of water are in a person whose mass is 75 kg?

• 50 kg water

• 72 kg water

• 94 kg water

• 150 kg water

The interest received on a savings account varies directly with the amount deposited. Daniel received $55.35 in interest on $1230 he deposited. How much interest would Daniel have received if he had deposited $2000 into his account?

• 34.04

• 90.00

• 1,285.35

• 44,444.44

y varies directly with the square of x.  If y=40 when x=4, find y when x = 7

• 17.5

• 70

• 122.5